Spatially programmable wave compression and signal enhancement in a piezoelectric metamaterial waveguide

We demonstrate high-precision dispersion tailoring in a metamaterial waveguide for wave compression and spatially tunable signal amplification. Spatial control over refractive index is achieved via digital controllers connected to piezoelectric unit cells. The digital shunt circuits allow numerically optimized circuit parameters to be uploaded directly to the experimental platform, enabling arbitrary spatial programming of the refractive index of the waveguide. Thus, the system acts as a reconfigurable piezoelectric array, altering the wavelength and group velocity of a given wave according to user specifications. In this work, optimizations are performed to implement gradual wave compression, realizing an effect analogous to that of an acoustic black hole. At the operating frequency of the design, the waveguide exhibits increased sensitivity and amplification of piezoelectric voltage output due to the compressed wavelength, shunt circuit resonance, and gradual variation in unit cell properties, avoiding internal reflections. Numerical and experimental results show that voltage amplification can be achieved in a desired position and frequency in the metamaterial waveguide.